1. Field of the Invention
The present invention relates to a capacitance type input detection device, a control method thereof, and a recording medium, particularly to a technique of detecting the moving direction of an operation member in a capacitance type sensor.
2. Description of the Related Art
In recent years, an electronic apparatus equipped with a display device, such as a cellular phone, a car navigation system, or a digital camera, uses a touch panel display which is operable as the user directly touches the display area by a finger. Various types, such as a capacitance type, a resistive type, and an optical type have been proposed to detect user input on such a touch panel. An appropriate detection type is selected in accordance with the application purpose of an electronic apparatus. In particular, the capacitance type is widely used because of its advantages in detection accuracy and multipoint detection.
The capacitance type touch panel display uses a method of detecting the capacitance component of a human to the earth, that is, detecting a capacitance change that occurs when an electrical conductor having the ground potential (GND) moves close to a sensor, as shown in, for example, FIG. 3A. The capacitance type sensing technique is applied not only to the touch panel display.
Assume a case in which a sensor electrode 301 serving as a sensor pattern and an electrical conductor 302 having the ground potential are provided, as shown in FIG. 3B. When an electrical conductor 303 moves close to the sensor electrode 301 and the electrical conductor 302 so as to overlap them, capacitive coupling occurs between the sensor electrode 301 and the electrical conductor 303 and between the electrical conductor 302 and the electrical conductor 303 so as to form a closed circuit, schematically shown in FIG. 3C. That is, when the electrical conductor 303 moves close to the sensor electrode 301 and the electrical conductor 302, the capacitance detected by a capacitance sensor IC 304 becomes larger than before capacitive coupling. Using this principle makes it possible to detect the presence of the electrical conductor 303 on the sensor electrode 301 with a larger capacitance when, for example, a plurality of sensor electrodes 301 are provided in an array within the movable range of the electrical conductor 303, and their capacitances can independently be detected.
Japanese Patent Laid-Open No. 2001-296966 discloses a method of detecting a rotation angle or a rotation direction in an input device for detecting a rotation input by detecting a capacitance change caused in electrodes arranged in the rotation direction by an electrical conductor that moves in accordance with rotation.
In the method of detecting the current position of an electrical conductor by detecting a capacitance change, as in Japanese Patent Laid-Open No. 2001-296966 described above, however, it is impossible to detect the initial position of the electrical conductor at the start of detection, for example, at the time of activation of an electronic apparatus having a capacitance type sensor. More specifically, in the conventional type, only when the capacitance has increased in the sensor electrode after a state change, the presence of the electrical conductor on the sensor electrode is detected. However, the initial position without a state change cannot be detected.
To enable initial position detection, a method of storing the capacitance of each sensor electrode with an electrical conductor existing above can be considered. However, this method is not realistic because the capacitance changes depending on a condition such as ambient temperature, or individual differences in electrical conductors or sensor electrodes.
If initial position detection is impossible, the moving direction of an electrical conductor from its initial position cannot be detected. That is, when the increase in the capacitance caused by movement is detected, the position where the moved electrical conductor exists can be grasped. However, since the initial position is unknown, the position from which the electrical conductor has moved to the position after movement cannot be grasped.
For this reason, in an electronic apparatus that detects the position of an electrical conductor moving in accordance with an operation member using a capacitance type sensor, conventionally, the first movement—that is, the movement of the electrical conductor from the initial position—needs to be ignored. That is, since the operation that has been done first after activation for the operation member is not reflected, the user may have the impression that the response of the operation system is slow.
The present invention has been made in consideration of the above-described problems, and has as its object to provide a capacitance type input detection device capable of grasping the moving direction of a detection target electrical conductor before and after movement, even if the position before the movement is unknown; a control method thereof; and a recording medium.